How to display a ProgressBar on a View while doing some work?

Question

I have a view with EditText, Button and ListView. Button's onClick() parses some site (this part works OK), but it takes some time to display the parsed info in ListView, so I want to display small ProgressBar on the place, where the ListView should take place after a while.

So, I add this to my layout (I write important part here):

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/layout1"
        android:weightSum="1.0">

        <EditText
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight=".86" />

        <ImageButton
            android:layout_height="match_parent"
            android:layout_width="0px"
            android:layout_weight=".14" />

    </LinearLayout>

    <RelativeLayout 
        android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:layout_below="@id/layout1"
        android:gravity="center"
        android:layout_centerInParent="true"
        android:id="@+id/progressbar" >

        <ProgressBar 
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            style="@android:style/Widget.ProgressBar.Small" />

    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/layout1">

        <ListView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" />

    </RelativeLayout>

</RelativeLayout>

In source code:

progressBar = (RelativeLayout) findViewById(R.id.progressbar);

And everytime I want to show the ProgressBar, I do this:

progressBar.setVisibility(View.VISIBLE);

for disabling:

progressBar.setVisibility(View.INVISIBLE);

But this doesn't work.

How can I work this out?

Answer 1

There's no need to manipulate your ProgressBar's visibility. ListView has a feature called "empty view" which is shown only if your ListView is empty. Here's what you need to do to use it:

1. If your activity extends ListActivity, use android:id="@android:id/list" for your ListView and android:id="@android:id/empty" for your ProgressBar.
2. If you don't extend ListActivity, there's a setEmptyView() method of your ListView, which lets you do the same thing.

The above method fits best if you don't need to empty your ListView (e.g. data is loaded only once, at the activity startup). If you need to set data after that, it is better to use ViewSwitcher, which also has great advantage - it lets you apply transition animation. For details on ViewSwitcher, take a look at this.